The inventive subject matter relates to power supply systems and methods and, more particularly, to uninterruptible power supply (UPS) systems and methods.
Data centers, industrial facilities, medical facilities and the like often have three-phase AC power distribution systems that are protected by UPS systems. Three-phase UPS systems may be used in such applications to provide backup power to maintain operation in event of failure of the primary utility supply. Three-phase UPS systems commonly have an “on-line” configuration including a rectifier and inverter coupled by a DC link that is also coupled to an auxiliary source, such as a battery, flywheel converter or other energy storage device.
A frequent goal in such applications is to provide uninterruptible power with high efficiency. Towards this end, on-line UPSs may support an “efficiency” mode in which the rectifier/inverter conversion chain is bypassed using a static switch when the utility source is within nominally acceptable bounds, so that power is not needlessly wasted in the rectifier/inverter chain. In addition, renewable sources, such as photovoltaic sources, may be coupled to the DC link of an on-line UPS to provide supplemental power, as described, for example, in U.S. Pat. No. 7,411,308 to Parmley and an article entitled “Photovoltaic UPS” by Jayasimha et al., IEEE TENCON 2003 Conference on Convergent Technologies for Asia-Pacific Region, vol. 4, pp. 1419-1423 (2003).